[U-Boot] [PATCH] ns16550: allow UART address to be set dynamically

[Wolfgang Denk]

Dear Graeme Russ,

In message <50CBB346.30208 at gmail.com> you wrote:
> 
> > And we already have a well-defined way to do this, which is the device
> > tree.  So any attempts to implement something different should be
> > reviewed very carefully.
> 
> I'm not sure I 100% get this, but from what I understand, the SoC (or maybe
> even some EEPROM on a particular board family) may contain device
> enumeration data in some vendor specific format (i.e. not in a device tree
> compatible format).

Yes, this may, and will, happen.  And we will have to support it.  The
question is, how to do that.  I definitely do not want to see any
uncontrolled growth of more and more such board or SoC specific code.

> The way I see it, there is no way that U-Boot can dictate to SoC and board
> vendors and say that data must be stored in DT format. So shouldn't U-Boot

We cannot dictate, but we can encourage and discourage such decisions.
If we communicate a clear position, we may even prevent ugly things
from happening.

> instead implement a board/SoC specific translation layer which converts
> this custom data into DT format (maybe in SPL if possible)?

Do you want to see each board grow it's own code to do that?  Because
this is the extreme that could result from such a decision, and I
seriously dislike any such thought.  Which is why I'm questioning the
general approach when I see it first.

> But the other problem is if this data includes console specific information
> (UART configuration). We are left blind until the DT functions become
> available. So maybe we need some small standard interface to allow the
> console to be configured early. But we need to prevent this from being
> abused (i.e. being used to do all kinds of hardware setting from the raw
> data and bypassing DT)

Why do we have to support such dynamic hardware configuration for a
very basic thing as the console port at all?

If the hardware designers cannot fix their minds and use a fixed
console port, they should be willing to suffer fromthe penalty that
they will have to use board specific board configurations that match
the actual consoles settings.  Why should we bend and do ugly stuff?
Just because software is so much easier to change than hardware?
I'm not going to buy this argument.

Best regards,

Wolfgang Denk

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